I don't know your exact climate or conditions. Why overseed? What equipment will you use--slit seeder? What type of grass do you intend to overseed? Tall fescue? What are the limiting factors? Snowmold? Is it irrigated?
Tall fescue probably belongs further south. As an overseed it is not a good choice because it may form clumps of wide blade grass in what (used to be) a nice bluegrass lawn. Weed seed is too high, could be poa. Other crop percentage is too high (that could be quackgrass).

Correct the situation that caused the turf thinness in the first place. I would go with a top-quality rye-blue mixture. KBG sometimes does not take well in an overseed situation because it is such a slow starter; the tiny seedlings don't get much light.

I don't consider myself a seed expert by any means but do hydroseed about 2 million sq. ft. a year and have for 16 years. I notice they do list that seed for use in PA also which is where I do most of my seeding. I have seeded all over and even once in Idaho. I personally would not be too impressed by that blend and would never consider using it on a lawn here. I guess my main dislike would be the tall fescue. I would rather see less fescue, more bluegrass and the fescues to be more creeping red and chewings. Perhaps just a bit more of a good quality rye as well. The price seems a little high as well. I do use Pennington seed but pay about $ 90.00 for a 50 pound bag. I do buy it right from Pennington by the pallet which you may be buying it through someone else which could affect the price.

You have one of the largest grass seed producers in the world right in your backyard. Jacklin Seed which is a division of Simplot is headquartered in Post Falls Idaho. If you need recommendations, it might be worth your time to contact them. Like Riggle is saying, there are some questions that need answered before any of us could help you with a specific seed choice. Jacklin produces many of the top NTEP varieties of turf grass. I don't know if you can buy directly from them but I'm sure they could point you to a distributor/wholesaler near you.

Below is a link to Jacklin Seed. It is an excellent tool to use for what you're asking. Choose the Zone you live in based on the map. Then choose what type of grass seed you need. They have overseeding mixes and blends. Hope this helps.

Below is a link to Jacklin Seed. It is an excellent tool to use for what you're asking. Choose the Zone you live in based on the map. Then choose what type of grass seed you need. They have overseeding mixes and blends. Hope this helps.

You are correct ...this area was once one of the main Mecas for grass seed production. Still much turf grass research going on here. Many of the local grass growers here have been pushed out of business due to bans on field burning and number of the former grass growing fields have been replaced with housing developments.

Potential clients have shown me quotes for aeration and over seeding [throw down seed] with low ball rates with ZERO mention of what grass seed is to be used.

Caddieshack II perennial rye was bred in northern Idaho--probably a good choice. Disease resistant. Per rye has good seedling vigor--so it will probably establish from seed in an overseed situation, even if conditions are not perfect, and even if you have strong competition from the previous established turfgrass. http://techsheets.simplot.com/Jacklin/caddieshack2.pdf

I would like this blend in my area for lawns that have annual problems with fungal issues.
Low on the KBG, higher on the tall fescues. Used something like it last fall for just such a lawn. Really came in nice.

For a general overseed though, would probably not use. Need to see more disease resistant KBG and reduce the tall fes on down.